From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753876AbcFPLRC (ORCPT ); Thu, 16 Jun 2016 07:17:02 -0400 Received: from mga04.intel.com ([192.55.52.120]:9705 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbcFPLRA (ORCPT ); Thu, 16 Jun 2016 07:17:00 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,480,1459839600"; d="scan'208";a="1003182117" Date: Thu, 16 Jun 2016 19:16:55 +0800 From: Haozhong Zhang To: Paolo Bonzini Cc: kvm@vger.kernel.org, rkrcmar@redhat.com, Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Gleb Natapov , Boris Petkov , Tony Luck , Andi Kleen , Ashok Raj Subject: Re: [PATCH v2 2/3] KVM: VMX: validate individual bits of guest MSR_IA32_FEATURE_CONTROL Message-ID: <20160616111655.ltcgle2cju2fksrx@hz-desktop> Mail-Followup-To: Paolo Bonzini , kvm@vger.kernel.org, rkrcmar@redhat.com, Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Gleb Natapov , Boris Petkov , Tony Luck , Andi Kleen , Ashok Raj References: <20160616060531.30028-1-haozhong.zhang@intel.com> <20160616060531.30028-3-haozhong.zhang@intel.com> <088f9fcb-a648-05d4-530a-790cb084bd09@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <088f9fcb-a648-05d4-530a-790cb084bd09@redhat.com> User-Agent: Mutt/1.6.1-neo (2016-05-02) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/16/16 12:01, Paolo Bonzini wrote: > > > On 16/06/2016 08:05, Haozhong Zhang wrote: > > +/* > > + * FEATURE_CONTROL_LOCKED is added/removed automatically by > > + * feature_control_valid_bits_add/del(), so it's not included here. > > + */ > > +#define FEATURE_CONTROL_MAX_VALID_BITS \ > > + FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX > > + > > +static void feature_control_valid_bits_add(struct kvm_vcpu *vcpu, uint64_t bits) > > +{ > > + ASSERT(!(bits & ~FEATURE_CONTROL_MAX_VALID_BITS)); > > The KVM-specific ASSERT macro should go. You can use WARN_ON. > will change to WARN_ON. > However, I think FEATURE_CONTROL_LOCKED should always be writable. If > you change that, it's simpler to just do |= and &= in the caller. > These two functions (add/del) are to prevent callers from forgetting setting/clearing FEATURE_CONTROL_LOCKED in msr_ia32_feature_control_valid_bits: it should be set if any feature bit is set, and be cleared if all feature bits are cleared. The second rule could relaxed as we can always present MSR_IA32_FEATURE_CONTROL to guest. I'm okey to let callers take care for the locked bit. > > + to_vmx(vcpu)->msr_ia32_feature_control_valid_bits |= > > + bits | FEATURE_CONTROL_LOCKED; > > +} > > + > > +static void feature_control_valid_bits_del(struct kvm_vcpu *vcpu, uint64_t bits) > > +{ > > + uint64_t *valid_bits = > > + &to_vmx(vcpu)->msr_ia32_feature_control_valid_bits; > > + ASSERT(!(bits & ~FEATURE_CONTROL_MAX_VALID_BITS)); > > + *valid_bits &= ~bits; > > + if (!(*valid_bits & ~FEATURE_CONTROL_LOCKED)) > > + *valid_bits = 0; > > +} > > + > > #define VMCS12_OFFSET(x) offsetof(struct vmcs12, x) > > #define FIELD(number, name) [number] = VMCS12_OFFSET(name) > > #define FIELD64(number, name) [number] = VMCS12_OFFSET(name), \ > > @@ -2864,6 +2897,14 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata) > > return 0; > > } > > > > +static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu, > > + uint64_t val) > > +{ > > + uint64_t valid_bits = to_vmx(vcpu)->msr_ia32_feature_control_valid_bits; > > + > > + return valid_bits && !(val & ~valid_bits); > > +} > > /* > > * Reads an msr value (of 'msr_index') into 'pdata'. > > * Returns 0 on success, non-0 otherwise. > > @@ -2906,7 +2947,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > > msr_info->data = vmcs_read64(GUEST_BNDCFGS); > > break; > > case MSR_IA32_FEATURE_CONTROL: > > - if (!nested_vmx_allowed(vcpu)) > > + if (!vmx_feature_control_msr_valid(vcpu, 0)) > > You can remove this if completely in patch 1. It's okay to make the MSR > always available. > But then it also allows all bits to be set by guests, even though some features are not available. Though this problem already exists before Patch 1, I prefer to leave it as was in Patch 1 and fix it here. Haozhong